Nick Clarke, who has died aged 58 of cancer, possessed one of the great voices of British broadcasting. From 1989 on BBC Radio 4, first on The World This Weekend and then as the leading presence on The World At One, he tried to get at the truth. He knew he could not paint the whole picture in every programme, but he got close. Intellectually courageous, scrupulously impartial, charming and unrelentingly polite, Nick used his array of qualities every day on every story.

He first made his mark on the Yorkshire Evening Post (1970-72), and as a passionate believer in public service broadcasting soon found his natural home at the BBC. He joined its north-west region as a reporter and industrial correspondent (1973-79), and then reported for BBC2's The Money Programme.

Undaunted by the economics and numbers of current affairs, he flourished from the time of his first reports on Newsnight in 1984, becoming its political correspondent and an occasional presenter. However, in 1989 he was recruited by Jenny Abramsky, at that time in charge of radio news and current affairs, and was an instant hit. He fell in love with Radio 4, and the audience reciprocated.

In 1994, he became the main presenter of The World at One, forming a strong partnership with the then editor, Kevin Marsh. They trusted each other and managed the trick of making the programme required listening in the Westminster village, while at the same time enlightening an audience of millions with no direct access to any political salon. The programme was persistent, and quite content to devote half- an-hour to a single political topic if they thought they had something new to add. This did not make the programme popular with all the politicians all the time, but Nick's sheer knowledge and unyielding civility subdued any rancour. He had no known enemies, only fans.

Born in Godalming, Surrey, he went to Bradfield college, Berkshire, and Fitzwilliam College, Cambridge, from which he graduated with a degree in modern languages. A widely-read man, he was a fanatical cricketer, if somewhat incurably hopeful about English prospects. When James Boyle, my predecessor but one as controller of Radio 4, revived Round Britain Quiz 10 years ago, Nick presided. He adored the programme: he and the contestants would spend a stimulating and mildly bibulous weekend (for he loved food and wine) recording the whole series. You could hear - yes, hear - the smile in his voice and the twinkle in his eye as he provided the clues and dispensed the points.

Cancer arrived in the autumn of 2005 and led to the amputation of a leg. Nick was remorselessly optimistic. The audience wrote in their thousands to wish him well. Then came a searing radio documentary with his wife, Barbara, about the treatment and its impact on his family.

For a while things looked good. Nick came back for a summer run of Any Questions and then The World at One. His first Any Questions outing was at a school in Tring, Hertfordshire. The audience in the hall knew it was his first programme since the cancer. When Nick came on to the platform there was a Radio 4 version of pandemonium. The walls vibrated to the sound of the clapping and stamping. Many people stood. Looking a little gaunt, Nick quietened them down and resumed his broadcasting where it had left off.

His journalistic hero was Alistair Cooke. Nick wrote his biography, and the obituary in the Guardian on March 31 2004; earlier this year he introduced on Radio 4's Book of the Week a previously unpublished Cooke work. Nick had many of the same attributes as his hero: a sublime voice, a mastery of language, an ability to paint a picture with astonishing economy, and above all a connection with the audience. We were lucky to have him.

He is survived by Barbara, their twin sons, and two sons and a daughter from his first marriage, which ended in divorce.

James Naughtie writes: Nick's bond with his audience was iron-clad. They knew his integrity for what it was, the mark of the man. At the microphone, as away from it, his personality glittered with that truth. Radio was perfect for him, because it always reveals the fakes in the end.

That mellow voice and his patience (even at the frequent moments of great exasperation on air) offered a kind of reassurance that was built on trust. If there was a story he would try to find it; if he was confronted by a charlatan he would reveal the fact with devastating calm. From the time we first worked together on The World At One in the late 80s, I knew him as a journalist of formidable judgment and as a person with the sterling values that too often our trade expunges in favour of egocentric frenzy.

I can see and hear him now - outside the Today studio at the start of his own working day, passing a wry observation about our choice of lead story, one quizzical eyebrow raised, and always worrying about the Test score; at lunch on a pavement in the Place des Vosges in Paris, where he seemed to become a native, chuckling over the latest Chirac ploy; late at night at a party conference, taking someone into a corner for a productive interrogation in the midst of all the joshing about who-was-getting-whom for our programmes the next day.

These are memories of a man who mattered. He embodied the best values of the BBC, nurtured by craftsmanship and decency, and he bore the despair of watching the passing managers and their fads with amused fortitude, knowing that they would be gone before long. He cared about words, about tone and about breadth, which is why he was drawn to write about Alistair Cooke.

That authenticity, which survived even the ravages of the last year, was unmistakable. It endeared him to an audience that knew what it was hearing, and among colleagues it made him much loved, perhaps even more than he knew.

· Nicholas "Nick" Campbell Clarke, broadcaster and writer, born June 9 1948; died November 23 2006